1. Field of the Invention
The present invention relate to an optical detection device and an optical device which uses the optical detection device. In particular, the present invention relates to an optical detection device for detecting an inclination of an optical axis of a light-capturing-receiving device and an optical device which uses the optical detection device.
2. Description of Related Art
Conventionally, there has been an optical detection device which divides a part of an optical beam y a beam splitter such that the divided optical beam should be received by an optical sensor such as a four-division detector so as to detect a direction of an inclination of the optical axis of the optical beam according to a position of a received optical spot. According to such a method, a part of the received light is used for detecting an inclination of the optical axis on regular basis when such a method is used for an aerial optical communication which has a function for capturing a light. Therefore, there is a disadvantage in that the intensity of the received light which is detected by the light receiving element may be reduced. In particular, in a long distance communication, the received light itself has a weak intensity. If a light for detecting an inclination is separated from such a light, the intensity of the light which is received by the light receiving element is extremely weak; thus, an S/N ratio may be reduced.
Here, a method is proposed for detecting a light in which an optical sensor such as a four-division detector is not used (for example, Japanese Unexamined Patent Application, First Publication No. Hei 5-122155). The device which is used for a method which is disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 5-122155 for detecting a light is provided with a vertical driving mirror 1 which is driven in a tilting manner in a vertical direction, a horizontal driving mirror 2 which is driven in a tilting manner in a horizontal direction, a light receiving lens 3, and a light receiving element 4. In order to detect and compensate the inclination of the optical axis by using this device, the horizontal driving mirror 1 and the horizontal driving mirror 2 are driven by a two-dimensional control by a control voltage at first. By doing this, the optical spot which is received on the light receiving element 4 describes a circular track while moving on the light receiving element 4. In such a case, the detected signal which is detected by the light receiving element 4 fluctuates periodically according to a degree that the optical spot exceeds from the light receiving element 4 as shown in FIG. 7. On the other hand, if the optical spot does not exceed from the light receiving element 4, the detected signal is constant. Therefore, it is possible to detect the light without loss by adjusting the angles of the mirrors 1 and 2 such that the level of the detected signal should not fluctuate. Therefore, the light receiving element 4 serves for detecting the shifting of the optical axis and the optical signals compatibly; thus, an element for decreasing the light amount is not necessary. Therefore, there is not a loss which is caused by the received light.
However, a high speed response is required to the light receiving element 4 for detecting the signals; therefore, it is necessary to reduce a capacity for the light receiving element 4; thus, the are for receiving the light is small in general. Also, it is a presupposition that a part of the optical spot must overlap in the light-receiving area so as to perform the detecting operation without losing the light; therefore, a range for detecting the shifting amount of the optical axis may be narrowed.
Therefore, it is a phenomenon in which it is not possible to deal with a case in which there is a wide range of the incident angle.